Less hypoglycemia with insulin glargine in intensive insulin therapy for type 1 diabetes. U.S. Study Group of Insulin Glargine in Type 1 Diabetes.

OBJECTIVE: Insulin glargine (21A-Gly-30Ba-L-Arg-30Bb-L-Arg-human insulin) is a biosynthetic insulin analog with a prolonged duration of action compared with NPH human insulin. This study compared insulin glargine with NPH human insulin in subjects with type 1 diabetes who had been previously treated with multiple daily injections of NPH insulin and regular insulin. RESEARCH DESIGN AND METHODS: This study was a multicenter randomized parallel-group study in which subjects were randomized to receive premeal regular insulin and either insulin glargine (at bedtime) or NPH insulin (at bedtime for patients on once-daily therapy and at bedtime and in the morning for patients on twice-daily therapy) for up to 28 weeks. Dose titration of both basal insulins was based on capillary fasting whole blood glucose (FBG) levels; the goal was a premeal blood glucose concentration of 4.4-6.7 mmol/l. RESULTS: A total of 534 well-controlled type 1 diabetic subjects (mean GHb 7.7%, mean fasting plasma glucose [FPG] 11.8 mmo/l) were treated. A small decrease in GHb levels was noted with both insulin glargine (-0.16%) and NPH insulin (-0.21%; P > 0.05). Significant reductions in median FPG levels from baseline (-1.67 vs. -0.33 mmol/l with NPH insulin, P = 0.0145) and a trend for a reduction in capillary FBG levels were achieved with insulin glargine. After the 1-month titration phase, significantly fewer subjects receiving insulin glargine experienced symptomatic hypoglycemia (39.9 vs. 49.2%, P = 0.0219) or nocturnal hypoglycemia (18.2 vs. 27.1%, P = 0.0116) with a blood glucose level <2.0 mmol/l compared with subjects receiving NPH insulin. CONCLUSIONS: Lower FPG levels with fewer episodes of hypoglycemia were achieved with insulin glargine compared with once- or twice-daily NPH insulin as part of a basal-bolus regimen in patients with type 1 diabetes.

Arachidonate metabolites and serotonin contraction of femoral arteries from DOCA-salt hypertensive rats.

Serotonin stimulates phospholipase A(2)(PLA(2)) leading to the production of prostaglandin products, several of which are vasoconstrictors. We hypothesised that the elevated vascular responsiveness to serotonin in deoxycorticosterone acetate (DOCA)-hypertensive rats is due in part to augmented production of vasoconstrictor cyclooxygenase products (e.g. PGF(2)alpha). Denuded helical strips of femoral arteries from DOCA-salt hypertensive rats (SBP 183 +/- 7 mmHg) and normotensive control rats (SBP 115 +/- 2) were used in all experiments. EC(50) values for several agonists were significantly reduced in DOCA arteries compared with controls (in mu mol/L, control vs. DOCA): PGF(2)alpha (0.99 vs. 0.23), PGE(2) (0.72 vs. 0.22), arachidonate (1.52 vs. 0.73), serotonin (0.19 vs. 0.07), noradrenaline (0.029 vs. 0.013), KCl (40.1 vs. 27.0 mmol/L) and AlF(4) (2.3 vs. 1.4 mmol/L). Treatment with indomethacin (14 mu mol/L) inhibited the responses to serotonin in DOCA arteries (EC(50) values 0.07 untreated vs. 0.70) and eliminated the responses to arachidonate but did not affect KCl or AlF(4-)contractions. Cyclooxygenase inhibitors shifted concentration response curves to serotonin in sham and DOCA tissues equally. Thus increased sensitivity to serotonin in DOCA arteries persisted following cyclooxygenase blockade. Therefore, although arachidonate products contribute to the serotonergic contraction in femoral arteries, the augmented response in arteries from DOCA hypertensive rats is not due to increased production of or sensitivity to cyclooxygenase products. Furthermore,arachidonate metabolites do not contribute to the contraction induced by either AlF(4-)or KCl in this preparation.

Comparative cardiovascular actions of clentiazem, diltiazem, verapamil, nifedipine, and nimodipine in isolated rabbit tissues.

Clentiazem is an 8-chloro-substituted derivative of diltiazem. We compared the relative potency of clentiazem with that of diltiazem, verapamil, nifedipine, and nimodipine in isolated rabbit right atria and vascular smooth muscle removed from various arterial beds. In experiments with isolated right atria, calcium channel blockers were added cumulatively to study relative cardiodepressive potencies (as compared with vascular effects) with the following results: verapamil greater than or equal to diltiazem greater than clentiazem greater than or equal to nimodipine much greater than nifedipine. The aorta, pulmonary, renal, mesenteric, coronary, and basilar arteries were removed, cut helically in strips, and mounted in isolated tissue baths to measure isometric force. Vessels were contracted with either 40 mM KCl (opening voltage-operated calcium channels) or 1 x 10(-5) M norepinephrine (NE, opening receptor-operated calcium channels). Cumulative dose-response curves were generated for relaxation with each calcium channel blocker. All compounds were more potent at relaxing potassium-induced contractions than NE-induced contractions. In vessels precontracted with KCl, neither diltiazem, verapamil, or nifedipine showed selectivity for basilar artery as compared with the mesenteric artery. Both clentiazem and nimodipine were selective (6- and 30-fold, respectively) for basilar artery in blocking potassium-induced contractions. When NE was used to contract the arteries, clentiazem (12-fold), diltiazem (8-fold), verapamil (8-fold), and nifedipine (153-fold) were all more potent in relaxing the contraction in basilar artery than in mesenteric artery. Nimodipine failed to demonstrate selectivity for basilar artery as compared with mesenteric artery contracted with NE.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of clentiazem on arterial pressure and renal function in normotensive and hypertensive rats.

The present study evaluated the effects of a new benzothiazepine calcium channel antagonist, clentiazem, on arterial pressure and renal function in spontaneously hypertensive rats (SHR), normotensive Wistar-Kyoto (WKY) and Munich-Wistar rats (MWR). Administration of clentiazem in doses from 1 to 20 micrograms/kg/min produced dose-dependent increases in sodium and water excretion in MWR, reaching maximum values of 292 and 376% of control, respectively, at the 20-micrograms/kg/min dose. Clentiazem (10 micrograms/kg/min) lowered arterial pressure by 16% and doubled glomerular filtration rate (GFR) in MWR. The rise in GFR was associated with an increase in glomerular capillary pressure of 16 mm Hg, produced by a combination of preglomerular vasodilation and efferent arteriolar vasoconstriction. In SHR, administration of clentiazem (10 micrograms/kg/min) lowered arterial pressure by 30 mm Hg and increased urine flow and sodium excretion by 137 and 200%, respectively. In WKY rats, the same dose of clentiazem decreased arterial pressure by only 10 mm Hg, whereas urine flow and sodium excretion increased 62 and 38%, respectively. A high dose of clentiazem (1 mg/kg bolus plus 1 mg/kg/hr infusion i.v.) lowered arterial pressure by 63 mm Hg in SHR. Renal vascular resistance fell by 39% and there was a 5-fold increase in sodium excretion. In WKY rats, the same dose of clentiazem reduced arterial pressure by 20 mm Hg, but it had no significant effect on sodium excretion. These results indicate that clentiazem increases sodium excretion and GFR in normotensive rats in part by preferentially dilating the renal preglomerular vasculature. This compound is also an antihypertensive agent that lowers arterial pressure and promotes sodium excretion in SHR.

[3H]TA-3090, a selective benzothiazepine-type calcium channel receptor antagonist: in vitro characterization.

Binding of the new benzothiazepine calcium channel blocker, (+)-(2S,3S)-3-acetoxy-8-chloro-5-(2-(dimethylamino)ethyl)-2,3-dihydro-2- (4- methoxyphenyl)-1,5-benzothiazepine-4-(5H)-one maleate, [3H]TA-3090), was characterized and its specificity for rat myocardial benzothiazepine receptors described. Scatchard plots and nonlinear regression analysis of specific [3H]TA-3090 binding best fit a one-site binding model (Kd = 8.8 +/- 2.7 nM, Bmax = 132 +/- 38 fmol/mg protein). Kinetically derived affinity constants were in close agreement (Kd = 7.86 nM) with those obtained from analysis of equilibrium binding data. In comparison, under identical conditions [3H]diltiazem exhibited a Kd of 38 nM and Bmax, 106 fmol/mg protein. Specific binding was saturable, reversible and stereoselective (d-cis-TA-3090 Ki = 14 nM; 1-cis-TA-3090 Ki = 2700 nM). Competitions for [3H]TA-3090 binding were conducted with nifedipine, propranolol, prazosin, quinuclidinyl benzilate, verapamil and yohimbine. Only the calcium channel blockers nifedipine and verapamil inhibited specific [3H]TA-3090 binding. Nifedipine could maximally inhibit only 52% of specifically bound [3H]TA-3090 at 10 microM. In contrast, however, 10 microM verapamil completely inhibited specific radioligand binding (Ki = 93 +/- 28 nM) but with six times less efficacy than TA-3090. Thus, these data demonstrate that [3H]TA-3090 is a potent radioligand selective for the benzothiazepine binding site and is consistent with the hypothesis that [3H]TA-3090 interacts with a myocardial benzothiazepine receptor site.

Central 6-hydroxydopamine and renal sodium retention in mineralocorticoid-treated rats.

Cerebroventricular administration of 6-hydroxydopamine attenuated the development of deoxycorticosterone hypertension in the rat but did not affect the initial period of renal sodium retention. However, escape from the sodium retention was greater in 6-hydroxydopamine-treated rats. These data support the hypothesis that destruction of central catecholamine-containing neurons influences the renal handling of sodium. The enhanced escape may lead to diminished total body sodium, which attenuates the development of deoxycorticosterone hypertension.

Mechanism of the pulmonary vasoconstrictor action of digoxin in the dog.

The pulmonary vascular effects of a subarrhythmic dose of digoxin (60 micrograms/kg i.v.) were examined in the canine in situ perfused lung. Digoxin produced an increase in pulmonary vascular resistance (66.1%) and pulmonary arterial pressure (8.2 mm Hg) at 70 min after injection in the constant-flow, blood-perfused lung preparation. The digoxin-treated group exhibited higher plasma levels of norepinephrine compared with control dogs. The pulmonary vasoconstrictor response to digoxin was abolished by prior treatment with the alpha-adrenergic antagonists phenoxybenzamine and phentolamine. This vasoconstriction does not involve inhibition of synthesis or action of vasodilator prostaglandins by digoxin, as pretreatment with indomethacin did not attenuate, and even tended to increase, the pressor response to digoxin. The response was prevented by prior treatment with blockers of nonneuronal uptake of catecholamines normetanephrine and hydrocortisone, but not with cocaine, a blocker of neuronal uptake. In the lung preparation perfused with Krebs buffer solution, digoxin failed to produce vasoconstriction when administered intravenously (60 micrograms/kg) or in the perfusate at a concentration of 8 ng/ml, the blood level at the peak of the pressor response. Sodium-pump activity (ouabain-sensitive 86Rb+ uptake) of intralobular pulmonary arteries excised after 90 min of exposure to digoxin was the same as activity in arteries from control dogs. In conclusion, digoxin produces a pulmonary vasoconstriction through an alpha-adrenergic mechanism. Since the pressor response was observed only in the blood-perfused lung, blood-borne catecholamines are apparently involved.

Effects of serotonin antagonists on blood pressure in mineralocorticoid hypertensive sheep.

The serotonin antagonist methysergide has a partial agonistic action on isolated vascular smooth muscle from hypertensive animals, whereas ketanserin, another serotonin antagonist, does not. The goal of this study was to determine the effects of these two agents on blood pressure in the conscious, deoxycorticosterone acetate (DOCA) hypertensive sheep. Adult sheep maintained on a standard laboratory diet and 0.1% NaCl/0.25% KCl drinking water developed hypertension following DOCA implantation (mean arterial pressure: control = 83 mm Hg, DOCA = 108 mm Hg). Methysergide (40 micrograms/kg--i.v. bolus) produced a greater pressor response in hypertensive sheep than in normotensive sheep (control = 8 +/- 1 mm Hg, DOCA = 18 +/- 3 mm Hg). Ketanserin (50 micrograms/kg--i.v. bolus), on the other hand, caused a similar decrease in blood pressure (approximately -16 mm Hg) in both control and DOCA sheep. Pressor responses to infusions of serotonin were greater in DOCA sheep compared with controls. Both methysergide and ketanserin were equally effective antagonists of a serotonin-induced pressor response (75% inhibition) in control and DOCA sheep. Methysergide had no effect on a norepinephrine-induced pressor response, but ketanserin caused a 20% attenuation of this response. These results demonstrate an enhanced responsiveness to serotonin and methysergide in DOCA hypertensive sheep.

Cerebral intraventricular 6-hydroxydopamine prevents vascular changes in the mineralocorticoid hypertensive rat.

The effect of cerebral intraventricular administration of 6-hydroxydopamine (6-OHDA) on blood pressure and vascular smooth muscle responsiveness in deoxycorticosterone acetate (DOCA)-treated rats was assessed. Rats treated with 6-OHDA and DOCA had significantly lower systolic blood pressures (142 +/- 8 mm Hg) than rats treated with DOCA alone (185 +/- 5 mm Hg). After 5 weeks of DOCA treatment, femoral arteries and aortae were excised from these rats, cut helically into strips, and placed in a muscle bath to record isometric force. Dose-response curves to serotonin were shifted to the left in femoral arteries from DOCA-treated rats compared to both control and 6-OHDA-DOCA-treated rats (ED50: DOCA = 6.8 X 10(-8) M, control = 27.9 X 10(-8) M, 6-OHDA-DOCA = 13.4 X 10(-8) M). Arachidonic acid, the prostaglandin precursor, produced greater maximal contractions in femoral artery strips of DOCA-treated rats (358 +/- 56 mg) than in those from controls (115 +/- 31 mg). The maximal response to arachidonic acid in arteries from 6-OHDA-DOCA rats (203 +/- 78 mg) was not different from control values. Ouabain produced a greater maximal response in aortic strips from DOCA rats (658 +/- 165 mg) compared to those from control (196 +/- 72 mg) or 6-OHDA-DOCA (309 +/- 87 mg) rats. We conclude that increased vascular responsiveness to serotonin, arachidonic acid, and ouabain in DOCA hypertensive rats is secondary to a central action of the mineralocorticoid.

Direct and sensitizing effects of serotonin agonists and antagonists on vascular smooth muscle.

Serotonin has several effects on vascular smooth muscle. In most vascular beds it causes vasoconstriction, but under the proper conditions it can cause vasodilatation. The constrictor response is a result of activation of specific receptors on the vascular smooth muscle, whereas the vasodilator response is mediated in part by the vascular endothelium. In addition to these direct effects on the vascular wall, serotonin can potentiate contractile responses to several other vasoactive agents (norepinephrine, angiotensin II, histamine, etc.). This indirect sensitizing action of the monoamine is probably mediated by activation of the S2 subclass of serotonergic receptors. These complex actions of serotonin on vascular smooth muscle may be altered in disease states such as hypertension.

Vascular responses to serotonin in steroid hypertensive rats.

This study investigates the mechanism responsible for increased vascular sensitivity to serotonin in deoxycorticosterone acetate (DOCA)-salt hypertension. Femoral arteries from normotensive and hypertensive rats were excised and cut into helical strips for isometric force recording. Dose-response curves to serotonin were shifted significantly to the left in arteries from DOCA-salt hypertensive rats compared to those from normotensive rats (ED50:DOCA = 7.1 X 10(-8) M; control = 27 X 10(-8) M). The partial agonistic properties of methysergide were increased in femoral arteries from DOCA-salt hypertensive rats. The competitive antagonism of serotonin by methysergide or ketanserin was similar in arteries from control and DOCA-salt hypertensive rats (pA2: methysergide, control = 10.4, DOCA = 10.5; and ketanserin, control = 10.4, DOCA = 10.4). After cellular calcium (Ca) depletion with EGTA, dose-response curves to Ca were obtained in the presence of serotonin (5.7 X 10(-5) M). The Ca sensitivity of vessels from hypertensive rats was not statistically different from that in arteries from normotensive rats. Contractile responses to serotonin in calcium-free solution following loading of a cellular store with Ca were 50% greater in arteries from DOCA hypertensive rats. These results suggest that the enhanced sensitivity to serotonin in DOCA-salt hypertensive rats is not related to a change in receptor affinity nor to an alteration in transmembrane movement of Ca following receptor activation. The increased serotonin sensitivity is related to an altered mobilization of Ca from a cellular store.

Vascular alpha-adrenergic blocking properties of quinidine.

The specificity of the alpha-adrenergic vascular blockade by quinidine was tested in the intact dog, in rabbit isolated aortic strips, and in rats under ganglionic blockade. Quinidine did not affect the pressor response of angiotensin II in dogs, the contractile response of histamine nor angiotensin II in aortic strips, nor the dose-pressor response curve of the alpha-agonist, B-HT 933 in the rat. However, the pressor effect of adrenaline and noradrenaline (NA) were significantly reduced in dogs, and the dose-response curves to NA in aortic strips and to the alpha-agonist, phenylephrine in rats was shifted to the right in a parallel manner by quinidine. In the rat, quinidine is at least 14 times more potent in antagonizing the vasopressor effect of an alpha 1-vs. and alpha 2-adrenoceptor agonist.

alpha-Adrenergic blocking properties of quinine HCl.

In the anesthetized dog, quinine HCl (50 mg/kg, i.v.) infused over a 20 min period produced 1 22% maximum decrease in diastolic blood pressure, a 53% increase in pulse pressure and a 52% increase in myocardial contractile force. The initial positive inotropic response was maximal in the first 5--15 min of the quinine infusion and decreased to near control levels 40 min following the quinine infusion. Quinine caused a marked reduction in the noradrenaline (NA) pressor response, blockade of the adrenaline (A) pressor response, partial blunting of the angiotensin II (AII) pressor effect but no change in the depressor effect of isoprenaline (I). The positive inotropic effects of CaCl2 were reduced and the duration of contractile action to both I and CaCl2 was significantly prolonged by quinine. In isolated rabbit thoracic aortic strips, quinine produced a parallel, dose-related shift of the concentration-response curve for NA to the right but did not affect the maximum responses. A pA2 of 4.91 was estimated by the method of Schild. The determined line had a slope of -0.84 which is similar to a theoretical slope of -1.0 and indicates a direct relationship between the number of receptors occupied and the contractile response. The responses to AII and histamine (H) were not altered by quinine. These results suggest that quinine HCl produces alpha-adrenergic blockade; additionally, quinine modifies catecholamine- and calcium-induced myocardial contractile force responses.